1. Field of the Invention
The present invention generally relates to electronic design automation. More specifically, the present invention relates to techniques and systems for detecting an occurrence of a shape which has been fractured into a configuration of primitive shapes which is different from a desired configuration.
2. Related Art
Rapid advances in computing technology can largely be attributed to improvements in semiconductor manufacturing technologies, which have made it possible to integrate tens of millions of devices onto a single chip. As part of the semiconductor manufacturing process, a photomask is used to expose a desired pattern on a multitude of semiconductor wafers. Therefore, printing a high-quality photomask is an important step of the semiconductor manufacturing process, because a printing error on the photomask can be propagated onto a multitude of semiconductor wafers.
Critical dimension (CD) variation on a printed photomask is an important measure of photomask quality. CD variation can be quantified as the measured deviation of a pattern on a printed photomask from the original mask pattern description. To produce a high-quality photomask, a mask pattern description typically contains a minimal number of shapes, with a minimal aspect ratio, a minimal number of slivers (i.e., shapes which are small in one or both dimensions), and a minimal number of edge slivers (i.e., slivers which are not sandwiched between other shapes).
Variable shaped beam (VSB) mask-making machines are only capable of writing a limited repertoire of geometric shapes onto a photomask, which typically consists of rectangles and trapezoids. A mask pattern description is processed using Mask data preparation (MDP) fracture software to fracture large and complex shape occurrences into fractured instantiations which contain only primitive shapes that the mask-making machine is capable of reproducing. When a multitude of occurrences of a complex shape exist on a mask pattern description, MDP fracture software may fracture the individual occurrences of the complex shape in different ways. This inconsistent fracturing across occurrences of a complex shape can increase the likelihood of a photomask printing error for the complex shape, and can introduce unnecessary CD variations on a photomask as a result of photomask printing errors.